Boris Johnson said that a Russian invasion of Ukraine would be painful, violent and bloody - Boris Johnson said a lightning war was possible but not unavoidable.
The prime minister said it would be disastrous if Vladimir Putin ordered thousands of soldiers to cross into Ukraine in 2014 in order to take further parts of the country after the annexation of Crimea.
Russia has mobilised 100,000 troops and heavy weapons on the Ukrainian border. As Nato strengthened its eastern borders with land, sea and air forces, tensions escalated further, as the White House and Downing Street announced that some diplomats were starting to be withdrawn from the country.
Johnson said he would be talking to political leaders in other capitals and Washington on Monday evening.
Johnson was asked about the possibility of an imminent invasion by Russian troops, speaking to broadcasters on a visit to a hospital. He said that the intelligence is pretty gloomy on this point.
There are 60 Russian battle groups on the Ukrainian border. Everyone can see that there is a plan for a lightning war that could take place in Kyiv. We need to make it clear to the Kremlin that that would be a disastrous step. Johnson said that he thought an invasion was not inevitable and that sense can still prevail, but he said that the UK was working with other countries to draw up a package of economic sanctions against Russia.
He said that if Moscow sent troops in, it would be a painful, violent and bloody business and I think it is very important for people in Russia to understand that this could be a new Chechnya. If forced, Johnson said he believed the Ukrainians would fight, and he said the Kremlin should understand that.
He said that the UK is in the lead in creating that package of economic sanctions, helping to strengthen the resistance of our Ukrainian friends with defensive weaponry that we resupplying and making it clear that we stand fully foursquare with the people of Ukraine. Russia's deputy foreign minister Alexander Grushko condemned Nato's buildup of soldiers earlier in the day, saying the military alliance was demonising Russia in order to justify military activity on Nato's eastern flank. The language of Nato is the language of threats and military pressure, he said in remarks published by Russian media.